1. Field Of The Invention
This invention relates to vehicle wheels and, more particularly, to light-weight non-pneumatic cone wheels.
2. Discussion Of The Prior Art
For well over a half a century, automotive vehicles have conventionally run on a two component assembly comprising a pneumatic tire mounted on a spoked or solid wheel. The drawbacks of these two-component assemblies are well-known and include, among other disadvantages, their cost, weight, and the susceptibility of the pneumatic tire component to blow-outs and punctures. In their search for a solution to these problems, the prior art has investigated a number of design approaches. Among the more promising are designs in which the wheel itself is sufficiently resilient to allow the pneumatic tire to be eliminated without sacrifice in acceptable life and riding and handling properties. An example of a resilient non-pneumatic solid one-component wheel in the prior art is the elastic conoidal wheel which is the subject of U.S. Pat. No. 3,698,461 invented by the inventor of the present invention and assigned to a common assignee. That prior art design had a hub and a resilient conoidally shaped body extending from the hub to a ground-engaging rim which served as the running surface of the wheel. In addition to a wheel of conoidal design, a convoluted cone wheel was also disclosed. A further teaching of a convoluted cone wheel in the prior art is the design disclosed by W. J. Hampshire in U.S. Pat. No. 4,350,196. Hampshire discloses a wheel assembly which has a hub and an integrally formed rim portion having a more-or-less S-shaped radial cross-sectional configuration. These prior art designs provide a practical resilient wheel that allows the pneumatic tire normally required to be eliminated without an appreciable sacrifice in riding comfort or vehicle handling characteristics. However, these prior art resilient wheels have a spring rate when deflected under load influenced by their required overload strength properties and thus advantage cannot be taken of the improvement possible with a resilient wheel which has a rate that can be varied with deflection under load. Non-pneumatic resilient wheels typically suffer from having an inadequate footprint for good highway handling properties if the structure must also endure the expected 3-g dynamic loading with ample fatigue life. In addition, the prior art does not provide means by which the spring rate of a conoidal wheel can be changed such that the operating characteristics of the wheel can be tailored to meet various requirements. The compromise of having adequate strength for dynamic overload conditions and adequate suppleness at 1-g for good handling has not been satisfactorily solved in the prior art.
Accordingly, it is an object of the invention to provide a vehicle non-pneumatic wheel structure having the service, ride, and handling performance characteristics similar to a conventional pneumatic tire and wheel assembly at loads up through the design load of the wheel structure.
A further object of the invention is to decouple the loads imposed by impact dynamics from a more supple resilient structure tailored for desirable handling properties at a nominal 1-g loading.
It is another object of the invention to provide a non-pneumatic wheel structure having mechanical functions and safety characteristics that are superior to those of a conventional pneumatic tire and wheel assembly at loads above the design load of a pneumatic tire and wheel assembly.
A yet further object of the invention is to provide a resilient non-pneumatic convoluted cone wheel capable of large deformation whose rate with deflection under load can be tailored to meet specific design objectives.
Yet another object of the invention is to provide a variable-rate resilient non-pneumatic convoluted cone wheel which is of unitary lightweight high-strength construction which can be designed to simulate the appearance of a conventional wheel and pneumatic tire assembly.
A further object of the invention is to provide a variable-rate resilient non-pneumatic convoluted cone wheel which has the mechanical functions and riding characteristics of a conventional wheel and pneumatic tire assembly but which has a lower rolling resistance.
Another object of the invention is to provide a resilient nonpneumatic wheel which is simple in design; economical to manufacture, operate, and service; and capable of withstanding static, fatigue, and impact loads compatible with expected service requirements.
Other objects and advantages of the present invention will become apparent to those skilled in the art from the description to follow when read in conjunction with the drawings appended hereto.